AUSTRALIA'S trouble-plagued Collins Class submarines - dubbed "dud subs" - were now the equal of conventionally powered submarines anywhere in the world, Prime Minister John Howard said today in Adelaide.

The multi-billion dollar vessels, which were supposed to be state-of-the-art when first built 10 years ago, have been best with problems. These included buoyancy issues, noise, leaks, and periscopes that would not focus properly.

But the Royal Australian Navy is confident all these glitches have been finally ironed out. And with new heavier torpedoes and sophisticated guidance systems, the Navy believes the six vessels will be able to perform at the level they were first intended for.

Mr Howard visited the Osborne facility today to mark the completion of modifications to the first of the vessels, HMAS Waller.

Mr Howard emerged form an hour-long tour of the Waller enthusiastic about the almost $1 billion price tag for the improvements.

"It is a reminder to me, and a reminder to the Australian public, of the enormous investment that is required to maintain an effective defence force for this country," he said.

"This will give us one of the most capable conventional submarines in the world," he said.

Long voyage to world class status

It's taken most of a decade but Australia's Collins submarines may finally be able to shed the "dud sub" tag.

Prime Minister John Howard today inspected HMAS Waller, the first of the Collins boats to be retrofitted with a computerised combat system similar to what's in use on US nuclear attack submarines.

The rest of the Collins fleet will progressively be refitted with this new system by the end of the decade under a remediation program launched in 2002.

It's been a long voyage but the Collins subs may at last demonstrate the complete range of capability envisaged when the project was launched back in the early 1980s.

In May 1983 the then Labor government invited tenders for a replacement diesel electric boat to replace ageing British-built Oberons which first entered service in 1967.

The winner was an Australianised version of the Swedish Kockums Type 471 with a contract for the deal worth about $5 billion signed in June 1987.

The Collins submarines were named after eminent World War Two fleet commander Vice-Admiral Sir John Collins (1899-1989).

The keel for HMAS Collins was laid at the brand new factory at Osborne, Adelaide, in February 1990. It was launched in 1993 and delivered to the navy in 1996.

The last of the six, HMAS Rankin, was delivered in 2001.

There may have been some brief thought about making the new submarines nuclear-powered but that was never seriously contemplated.

Instead, the Collins boats are powered by electric engines while underwater and large diesel motors while surfaced. The diesels also charge a vast bank of batteries.

This technology makes the Collins boats not all that different from the German U-boats which waged war in the North Atlantic during World War Two - except in one crucial area.

That was the decision from the outset to equip the Collins boats with a computerised combat system.

The plan was to link together the sensors (sonar arrays, periscope and radar) communications, navigation and weapons systems so that a sailor sitting at a console in the control could manage all vital functions.

Unsurprisingly, this didn't work very well. Through the 1990s the delays accumulated as scientists struggled to integrate the disparate elements of this system and get them to all operate in harmony.

Worst of all, the Collins boats were too noisy, a potential death sentence for a vessel intended to operate in near total silence.

The navy well knew about all these problems - and so too did the taxpayers of Australia on October 8, 1998 when the Sydney Daily Telegraph published its infamous "Dud Subs" story which, among other claims, suggested the Collins boats made as much noise as a rock concert.

Justified or not, this served to focus the government's attention. Then defence minister John Moore commissioned Malcolm McIntosh and John Prescott to review the problems and propose a way forward.

They reported in June 1999. By this stage various fixes were under way. The US Navy came to the party, allowing use of its underwater acoustic test range to isolate noise problems which have now been fixed.

The US Navy also provided some black boxes to augment the combat system to make it at least usable.

McIntosh and Prescott noted that the combat system remained the principal technical challenge to be resolved. They concluded that only so much could be achieved with the legacy system.

One observer explained it in computer terms - Collins was stuck with 286 equivalent processors when the world had moved on to Pentiums.

In 2002, the government approved a replacement combat system, opting for the Raytheon CCS Mark II tactical command and control system, known in US service as AN/BYG-1, in a contract worth $444 million.

This had the effect of cementing the already very close links with the US Navy.

With the new combat system will come new heavyweight torpedoes, the Mark 48 ADCAP (advanced capability), an improved version of the existing Mark 48 torpedoes.

Each weighs 1.6 tonnes, has a range of more than 40 kilometres and can sink almost any vessel afloat. The Federation of American Scientists website suggests a price of $US3.5 million each.